Oleanane triterpenoids

Fig. (3). Tetranor-cycloartane and oleanane triterpenoids isolated from Astragalus sp.

The selective oxidation of oleanane triterpenoids by a Cr03-py-BunOH-HaO-derived reagent has been studied.119 Some reactions of glycyrrhetic acid have been... 

Oleanane triterpenoids are the largest group within the triterpenes and encompass a huge number of active compounds. They are structurally classified as olean-12-ene (Table 2) and ll-keto-olean-12-ene (Table 3), directly derived from the oleanane skeleton. Other modifications give rise to the D C-friedooleananes (Table 4), friedelanes (D A-friedooleananes), 24-nor-D A-friedooleananes (Table 5) and 24,30-dinor-D A-friedooleananes (Table 6). The oleananes include glycyrrhetinic acid, probably the most widely studied triterpene. 

The plant is known to produce norbisabolane diterpenes, including phyllanthusols A and B, which are both cytotoxic (36). From the bark, pentacyclic triterpenoids, phyl-lanthol, and olean-12en-3[3-ol (p-amyrin) have been isolated (37). Note lupane- and oleanane-type triterpenoids isolated from the bark of Phyllanthus flexuosus, such as olean-12-en-3 (3,15 a-diol, olean-12-en-3 [3,15 a,24-triol, lupeol, and betulin inhibited the enzymatic activity of topoisomerase II activity with IC50 values in the range of 10 to 39 p.M (38). 

Sakai K, Fukuda Y, Matsunaga S, Tanaka R, Yamori T. New cytotoxic oleanane-type triterpenoids from the cones of Liquidamber styraciflua. J Nat Prod 2004 67 1088-1093. 

Frankincense, also known as olibanum, is obtained from trees belonging to the genus Boswellia (Burseraceae family). It is one of the best-known ancient plant resins. The ancient Egyptians were the first to use it as incense in embalming practices and in the preparation of medicines, cosmetics and perfumes, and today it is still used therapeutically. It contains pentacyclic triterpenoids belonging to oleanane, ursane or lupane type molecules and in particular of a- and p-boswellic acids, and their O-acetates [104 111], 11 -Oxo-p-boswellic acid and its acetyl derivative, identified in several Boswellia species, are also diagnostic for frankincense [112]. 

Figure 5.5 Norrish reaction of a triterpenoid (e.g. dammarane, oleanane or ursane type) leading to ring opening and subsequent oxidation of the ketone to the corresponding acid...

Triterpenoid saponins are synthesized via the isoprenoid pathway.4 The first committed step in triterpenoid saponin biosynthesis involves the cyclization of 2,3-oxidosqualene to one of a number of different potential products (Fig. 5.1).4,8 Most plant triterpenoid saponins are derived from oleanane or dammarane skeletons although lupanes are also common 4 This cyclization event forms a branchpoint with the sterol biosynthetic pathway in which 2,3-oxidosqualene is cyclized to cycloartenol in plants, or to lanosterol in animals and fungi. 

In our study on the chemical constituents of Salvia frigida Boiss., we report here the isolation and identification of two oleanane type (componnd 1, 2) and two cycloartane type triterpenoids (compound 3,4) with the componnds a-amyrin 5 and P-sitoserol 6. The compounds have been characterized by UV/vix, IR, H NMR, NMR and MS spectroscopy. 

Some oleanane type triterpenoids with highly oxygenated were isolated form Barringtonia racemosa as shown in Fig 6. Six friedelane type triterpenoids were isolated from bark of Hibiscus tiliaceus collected from Flainan province as shown in Figure 7. 

Gowri, P. M, Radhakiishnan, S. V, Basha, S. J, Sarma, A. V, Rao, J. M. Oleanane-t)rpe isomeric triterpenoids from Barringtonia racemosa. Journal Natural Product. (2009). 

Tissue cultures of Isodon japonicus could biosynthesize oleanane- and ursane-type triterpenoids from [4-13C]MVA with sufficient incorporation of tracer to allow the elucidation of the labelling pattern by 13C n.m.r. spectroscopy.356 The results verify the hypothesis of Ruzicka involving cyclization of 2,3-oxidosqualene in a chair-chair-boat form, followed by specific 1,2-hydride shifts, and the rearrangement of... 

Papers have appeared on the effect of different reagents on the course of the dehydration of the 3/3-hydroxy-group of acacic acid lactone and related pentacyclic triterpenoids,the ring A conformation of 2-methyl-3-hydroxy- and 2-methyl-3-oxo-derivatives of 19/3,28-epoxy-18a-oleananes, the use of lead... 

Plant-derived triterpenoids are overtly abundant in sediments from the late Mesozoic onwards. These include oleanane (61), lupane (62), and taraxastane (63). There is a clear relationship between these compounds and triterpenoid precursors such as /3-amyrin (64)... 

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